Electrical precipitation



April 29, 1952 H. RICHARDSON 2,595,204

ELECTRICAL PRECIPITATION NOV- 25, 1949 2 SHEETS-SHEET 1 H. L. RICHARDSON ELECTRICAL PRECIPITATION April 29, 1952 2 SHEETSSHEET 2 Filed NOV. 25, 1949 Patented Apr. 29, 1952 UNITED STATES PATENT OFFICE ApplicationNovcmbier 25. 1949,? Serial No. 129,340 A '3'Claims. lei. 183-1) This invention'relates'to a method and apparatus'for electrical lprecipitation. It is more particularly directed to a method and means for' effectively recovering collected material from electrical precipitators of the Cottrell type.

Diiiiculties frequently encountered in trying to obtain high efiiciences in the cleaning of gases by presently available methods and apparatus for electrical precipitation are often due not to lack of emciency in the fundamental processes of ionization and precipitation of the suspended ma-- terials but to redispersion of the precipitated material in the gas stream in the course of re moval of the material from the collecting electrode surfaces. ing electrode structures have been devised and put into practical operation for the purpose of overcoming losses of efliciency due to redispersion' of the collected material in the gas stream but difiiculties with this problem still remain.

It has now been found that greatly improved efilciencies of gas cleaning can be obtained particularly when dealing with suspended particles difficult to remove with high efiiciencies, by vibrating the collecting electrode structures of ,the electrical precipitors, preferably substantially continuously throughout the precipitation opera} tion, at a relative low intensity which can be most conveniently measured and specified in terms .of the acceleration imparted to the collecting electrode structure, as measured by an accelerometer measuring acceleration in effective (root mean square) values.

In general, the most effective intensity of vibration for high over-all collection efiiciency has been found to be an intensity corresponding to an acceleration of the order of to 100 inches per second per second, and with most materials intensities of vibration corresponding to accelerations below about 50 inches per second per second are preferable. In general, the lower intensities are preferable, not only because they give higher over-all collection efliciencies with a greater range of materials and conditions of operation but because they involve lower power consump-- tion and impose much lower stresses on the precipitator construction, reducing wear and structural looseness. The intensities of vibration used in the method of the invention are characterized .by imparting an effective (root mean square) 'acceleration substantially less than the acceleration of gravity (g=approximate1y 385 inches per second per second).

The principles of the invention may be applied to any type of collecting electrode such as unperforated plates, perforated single and multiple Many different forms of collect-y .2 plates, corrugated plates,'rod curtain asseinbliis. v member assemblies and the like. It is desirable that the collecting electrode structures be suspended in such a manneras to permit relatively free vibration. The 'vibratingdevicemay be any of the common types of magnetic, "mechanical, or air vibrators. The vibrators'are preferably connected rigidly to the collecting electrode structures at or above their vertical midpoints. The frequency of vibration is not critical, although it is preferred "to use a "relatively-{high "frequency of vibration maintained-substantially throughout the o erating period Ofth precipi- In order to obtain the highest i'efliciericis, particularly in the treatment of gases containing difficultly removable materials, it is desirable that the gas velocity should not be too high. Velocities of the order of 6.5 to'- 7:5 feet per second are suitable for most materials, with a total time of treatment of the order of 2 to 3 seconds. Energizing currents of the order of 15 to 30 milliamperes per 1000 ft. g discharge electrode length have been found to be suitable.

For the purpose of illustrating the principles of the invention, a typical embodiment of the invention will be merely particularly described with reference to the accompanying drawing in which:

Fig. 1 is a side elevation of an electrical precipitator embodying the principle of the invention with a portion of the wall broken away;

Fig. 2 is an elevation of the precipitator of Fig. 1 with a portion of the end wall broken away; and

Fig. 3 is an enlarged isometric perspective showing a section of complementary discharge and collective electrode systems of the precipitator of Fig. 1.

In the drawings i0 is the precipitator shell having gas inlet and outlet l l and I2 respectively and bottom hoppers l3 for receiving collected material, and suitably positioned inspection doors l4.

Supported from the shell structure by means of I-beams l5, brackets I6, and hanger rods I'I loosely suspended in the brackets by means of nuts II, are a plurality of parallel collecting electrode plates 58, loosely connected at their bottom ends by link spacers l9.

Between adjacent collecting electrode plates, discharge electrode wires 20 are suspended from horizontal bars 2| attached to high tension frame 22. The wires are maintained in position by horizontal spacer bars 2| and are held taut by weights 23. The discharge electrode system is suspended from insulators 24 through which a conductor passes to maintain the discharge elec trodes at a high potential with respect to the collecting electrodes.

A vibrator bar 25 extends along each section of collecting electrode plates I 8 being tack-welded or otherwise connected to each plate in the section. The vibrator bar passes through the shell of the precipitator and is attached to a vibrator device 26, adapted to subject the collecting'electrode structure through the bar 25 to vibration, the intensity of which is equivalent to an efiective acceleration substantially less than g.

The construction shown by way of example in the drawings for the purpose of illustrating the principles of the invention is not intended to limit the scope of those principles. The invention may be applied in a wide variety of ways within the scope of the claims. For example, the vibrating force may be applied in the plane of extension of the collecting electrodes rather than at right angles thereto as shown in the drawing and the vibrator devices may be mounted in other positions, for example, in the upper portion of the precipitator shell, The particular form of precipitator and collecting and discharge electrode structures are merely illustrative and the invention may be applied to any precipitator structure having extended collectingelectrode surface structures.

I claim:

1. In an electrical precipitator including dis-l effective to vibrate the collecting electrode structure at a controlled intensity equivalent to an effective acceleration substantially less than 9.

2. In an electrical precipitator including discharge electrode means and complementary extended surface collecting electrode structures loosely suspended in the precipitator in spaced relation to the discharge electrode means, a vibrator rigidly connected to the collecting electrode structure'efi'ective to vibrate the collecting electrode structure at a controlled intensity equivalent to an effective acceleration of from about 10 to about 100 inches per second per second.

3. In an electrical precipitator includingdischarge electrode means and complementary extended surface collecting electrode structures looselysuspended in the precipitator in spaced relation to the discharge electrode means, a vibrator rigidly connected to the collecting electrode structure efiective to vibrate the collecting electrode structure at acontrolled intensity equivalent to an effective acceleration not exceeding about inches per second per second.

HARRY L. RICHARDSON.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Germany Apr. 5, 1939 

